• Korean Journal of Biological Psychiatry
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• v.2 no.1
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• pp.107-114
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• 1995

This study was to investigate the anatomical evidence of anxiety. MRI was used to study 11 patients with panic disorder and 15 patients with complex partial seizure, and 21 controls. The regions of interest in the MRI were measured with computer-assisted planimetry using the AutoCad and digitizer. The following results were obtained ; 1) The mean age was 49.7(12.4) years in patients with panic disorder and 30.1(7.5) years in patients with complex partial seizure. 2) There were na signi ficant differences between 3 groups in the values of cerebral area, temporal lobe, caudate nucleus, hippocampus, parahippocampus, amygdala, third ventricle and VBR. The right parahippocampal region which attracted most attention in neurobiological studies regarding anxiety, tended to be larger in both study groups compared to the control group, but with no statistical significance. 3) There was lett-right reversal of temporal lobes in both study groups. And these are mainly due to asymmetrical increase in area of the temporal lobe on right side. These results suggest that temporal lobe, especially right temporal, is the anatomical correspondence of anxiety and functional activation of temporo-limbic system may be accompanied by the structural change of temporal lobe.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.10
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• pp.722-733
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• 2006

In scalable streaming application, there are two important knobs to tune to effectively exploit the underlying network resource and to maximize the user perceivable quality of service(QoS): layer selection and packet scheduling. In this work, we propose Semantics Aware Packet Scheduling (SAPS) algorithm to address these issues. Using packet dependency graph, SAPS algorithm selects a layer to maximize QoS. We aim at minimizing distortion in selecting layers. In inter-frame coded video streaming, minimizing packet loss does not imply maximizing QoS. In determining the packet transmission schedule, we exploit the fact that significance of each packet loss is different dependent upon its frame type and the position within group of picture(GOP). In SAPS algorithm, each packet is assigned a weight called QoS Impact Factor Transmission schedule is derived based upon weighted smoothing. In simulation experiment, we observed that QOS actually improves when packet loss becomes worse. The simulation results show that the SAPS not only maximizes user perceivable QoS but also minimizes resource requirements.

• Journal of Digital Contents Society
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• v.16 no.2
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• pp.275-282
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• 2015

Since starting of terrestrial digital broadcasting in 2001, there has been discussion on introduction of multiple broadcasting services, one of advantages of digital broadcasting. In the mean time, task force on terrestrial multiple channel experimental broadcasting was formed with government organizations, broadcasting companies and household appliance companies in Oct. 2013, and terrestrial multiple channel experimental broadcasting was started between Jan. to April, 2014. Based on this experimental result, EBS started 2HD MMS experimental broadcasting first in Korea on Feb. 11, 2015. This study was carried out in consideration of operation of 2 HD channels in existing 6MHz bandwidth based on MPEG-2 codec with development of compression technology. A study on image quality optimization was carried out and applied to 2HD MMS experimental broadcasting through application experiment of variable bit rate and change according to 1080i and 720p scanning type.

• Journal of Communications and Networks
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• v.3 no.4
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• pp.383-395
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• 2001

Recent measurement and simulation studies have revealed that wide area network traffic displays complex statistical characteristics-possibly multifractal scaling-on fine timescales, in addition to the well-known properly of self-similar scaling on coarser timescales. In this paper we investigate the performance and network engineering significance of these fine timescale features using measured TCP anti MPEG2 video traces, queueing simulations and analytical arguments. We demonstrate that the fine timescale features can affect performance substantially at low and intermediate utilizations, while the longer timescale self-similarity is important at intermediate and high utilizations. We relate the fine timescale structure in the measured TCP traces to flow controls, and show that UDP traffic-which is not flow controlled-lacks such fine timescale structure. Likewise we relate the fine timescale structure in video MPEG2 traces to sub-frame encoding. We show that it is possibly to construct a relatively parsimonious multi-fractal cascade model of fine timescale features that matches the queueing performance of both the TCP and video traces. We outline an analytical method ta estimate performance for traffic that is self-similar on coarse timescales and multi-fractal on fine timescales, and show that the engineering problem of setting safe operating points for planning or admission controls can be significantly influenced by fine timescale fluctuations in network traffic. The work reported here can be used to model the relevant characteristics of wide area traffic across a full range of engineering timescales, and can be the basis of more accurate network performance analysis and engineering.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.4
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• pp.10-14
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• 2009

We propose a trapezoidal gate AlGaN/GaN high electron mobility transistor(HEMT) to improve the breakdown voltage characteristics and its feasibility is investigated by two-dimensional device simulations. The use of a trapezoidal gate structure appears to be quite effective in dispersing the electric fields concentrated near the gate edge on the drain side from the simulation result. We find that a peak value of the electric field along the 2-DEG channel is reduced by 30%, from 4.8 to 3.5 MV/cm and thereby, the breakdown voltage(Vbr) of the proposed AlGaN/GaN HEMT is increased by about 40%, from 49 to 69 V, compared to those of the standard AlGaN/GaN HEMT.

• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.1009-1022
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• 2004

Smoothing is a transmission plan where variable rate video data is converted to a constant bit rate stream. Among them are CHA, MCBA. MVBA, e-PCRTT and others. E-PCRTT algorithm, which was improved from PCRTT, restricts the number of rate changes with fixed-size run. This causes unnecessary rate changes and may not guarantee QoS when buffer size is small. In this paper. a smoothing algorithm is pro-posed, where the number of rate changes are not limited and the size of run can be flexible, in order to overcome the shortcomings of e-PCRTT. Experiments demonstrated that the proposed algorithm such as e-PCRTT. In order to show the performance, var-ious evaluation factors were used such as the nember of rate changes, buffer size to maintain QoS, and so on.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9A
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• pp.837-843
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• 2006

IEEE802.15.3 and IEEE802.15.4 have defined the hybrid MAC protocols based on TDMA and CSMA where a multi-frame TDMA structure is employed so that multiple data frames can be transmitted within one timeslot to guarantee minimum delay bounds of isochroous traffic. However, TDMA has an intrinsic problem that cannot dynamically allocate optimal length of timeslot to each station. Therefore the idle timeslot can be produced by stations when each transmission queue is instantaneously empty during its timeslot, which would waste lots of timeslots especially in the multi-frame TDMA systems. In this paper, we propose a more flexible multiple-access scheme for the multi-frame TDMA system based on the concept of virtual slot which is accessible by every station with the highest priority for slot owner and lower priority for other stations. Finally, our simulation results from various environments show that proposed scheme can achieve magnitude improvement of total system throughput and average message delay by maximizing channel utilization.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1A
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• pp.132-141
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• 2000

In this paper, we proposed the MAC protocol of APON supporting multi-class traffic such as CBBUVBR, ABR, UBR, to guarantee the required QoS of each service. For this, we analyze the performance of variousrequest mechanisms and employee the different request mechanism for each traffic classes. Upstream anddownstream frame structures to minimize transmission overhead are proposed based on our request mechanism.The proposed MAC protocol applies the different priority to permit distribution process. CBBWBR traffic, withthe stringent requirements on CDV or delay, is allocated prior to any other class. ABR traffic, which hasnon-strict CDV or delay criteria, uses flexibly the available bandwidth but ensures a minimum cell rate (MCR).UBR traffic is allocated with lowest priority for the remaining capacity. The performance of proposed protocol isevaluated in terms of transfer delay and 1-point CDV with various offered load. The result of simulation showsthat the proposed protocol guarantees the required QoS of the corresponding category, while making use of theavailable resources in both an efficient and dynamical way.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.2042-2051
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• 1998

VBR compressed, pre-recorded video is known to exhibit significant, multiple time-scale bit rate variability. To reduce the variability and burstiness of the aggregated transmission rate as low as possible, in this paper, we present an adaptive bandwidth smoothing algorithm, that can be effectively applicalble for VoD services over a shared-medium channel. For these environments where many clients are connected to a single server, by introducing the conventional MVBA(minimum variability bandwidth allocation) algorithm and controlling adaptively the conventional MVBA(minimum variability bandwidth asllocation) algorithm and controlling adaptively the aggregated transmission rate whenever a new clients request is arrived at the server side, the proposed algorithm effectively reduces the burstiness and variability of the aggregated transmission rate. Through computer experiments, it is shown that the proposed method perporms better than the convertional non-aggregated bandwidth smoothing schemes in terms of the peak rate, standard deviation, number of rate changes for the aggregated traffic.

• Journal of Digital Contents Society
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• v.16 no.5
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• pp.775-781
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• 2015

EBS started 2HD MMS experimental broadcasting for the first time in Korea on Feb. 11, 2015. It uses the picture compression technique based on MPEG-2 CODEC, and applies the result of the experiment about variable bit rates and changes according to the scanning types, 1080i and 720p. But when changing channels, the delay in displaying picture occurs because of the operation of the variable GOP on MMS broadcasting, which optimizes image quality by application variable bit rates. In this study, verified the relationship between the decoding time of I frames and the GOP set in the encoding step by experimenting and analyzing ON-AIR TS. By using the verification data and adjusts the Encoder GOP parameters, improved the different video display time delays according to the scanning mode 1080i and 720p.